On the other hand, in heterotic string theory, there have been the studies of the string vacua with
cosmological constants exponentially suppressed with respect to some continuous parameter expressing the `distance'
from the SUSY vacua
(for instance, the radii of tori of compactifications as given in [1]})
in [2]}, [3]}, and more recently, e.g in [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]} from the various viewpoints of model building in string phenomenology.
